The present invention relates generally to high temperature superconducting (HTSC) filter systems for use in, for example, cellular PCS systems and, more particularly, to tower mountable HTSC filter systems and enclosures.
Recently, substantial attention has been devoted to the development of high temperature superconducting radio frequency (RF) filters for use in, for example, cellular telecommunications systems. However, such filters are extremely temperature sensitive, and the use of such filters within tower mounted communications systems can raise significant heat management issues.
One such issue, is the issue of cryocooler xe2x80x9ccold fingerxe2x80x9d temperature regulation, which is addressed in co-pending, U.S. patent application Ser. No. 09/204,897, filed on Dec. 3, 1998 and entitled xe2x80x9cTEMPERATURE CONTROL OF HIGH TEMPERATURE SUPERCONDUCTING THIN FILM FILTER SUBSYSTEMS,xe2x80x9d the disclosure of which is incorporated herein by reference.
However, another equally important issue, and one that is addressed herein, is the issue of heat dissipation. Stated somewhat differently, for an HTSC filter system to function properly, the heat of compression generated by a cryocooler incorporated within the system must be efficiently and reliably rejected to the ambient environment. If that heat cannot be efficiently and reliably rejected, it may have a serious impact upon system operation and, depending upon the circumstances, could result in inefficient cryocooler operation and/or cryocooler shut down.
Those skilled in the art also will appreciate that, when multiple HTSC filters are deployed, for example, within a dewar cooled by a cryocooler, and the cryocooler is mounted, for example, on a telecommunications tower, substantial durability and reliability issues may arise. For example, when a system is to be mounted at the top of a tower, the system must be able to withstand significant changes in climate and weather, and the system must be reliable and require minimal maintenance. In this latter regard, reliability can be improved, and maintenance requirements reduced, through the use of a minimal number of moving parts. Thus, where a cryocooler and associated HTSC filter system are to be mounted atop a tower, it would be desirable to utilize a cryocooler including as few moving parts as is possible. Similarly, any associated heat management system should include a minimum number of moving parts.
In view of the foregoing, it is believed that those of ordinary skill in the art would find an improved system for xe2x80x9cmanagingxe2x80x9d the heat of compression generated by a cryocooler within a tower-mounted HTSC filter system to be quite useful. It also is believed that those skilled in the art would find a tower-mounted HTSC that is highly reliable and utilizes a minimum number of moving parts to be useful.
The present invention is directed to an improved heat management system and design for a tower-mounted HTSC filter system.
In one particularly innovative aspect, a tower-mounted HTSC filter system in accordance with the present invention utilizes a plurality of heat pipes to carry heat away from a cryocooler body to a finned heat dissipation assembly. Moreover, an HTSC filter system in accordance with the present invention may comprise a environmentally sealed housing having, for example, a Stirling cycle cryocooler and dewar assembly mounted therein, a heat dissipation assembly coupled to a selected surface of the environmentally sealed housing, and a plurality of heat pipes providing a thermal coupling between the heat dissipation assembly and one or more heat rejecting blocks of the cryocooler.
In a presently preferred embodiment, the heat pipes comprise sealed stainless steel tubes that are filled with ammonia, and the environmentally sealed housing comprises a double-walled aluminum cylindrical container.